Concentrations and seasonal trends of extracellular microcystins in freshwaters of the Czech Republic results of the national monitoring program

The first outcomes of the national monitoring program on cyanobacteria and their toxins in the Czech Republic are reported. The concentrations of extracellular microcystitis (MCs, analyzed by ELISA) in 206 water samples collected from 94 localities have been investigated. Observed MC concentrations were relatively high in comparison with the literature data, although weather conditions during the covered season (year 2004) were less favorable for the cyanobacterial water blooms. Detectable MCs (>0.1 25 mu g/L) were found in 145 waters (70% of all samples) with a median concentration of 0.67 mu/L. The total median, including samples with no detectable MCs, was 0.26 mu g/L. The seasonal trend showed an increase from July to September at most localities (maximum concentrations of about 8 mu g/L and extremes up to 37 mu g/L). However, a peak at the beginning of the season or continuously elevated MC concentrations were also observed at some localities. Positive correlations between increasing concentrations of MCs and the dominancy of Microcystis spp. have been observed. The survey provides the first large-scale study of the occurrence and seasonal variability of extracellular microcystins that are of particular interest for drinking water management.